/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.netease.arctic.flink.util;

import javax.annotation.Nullable;
import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Serializable;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;

/**
 * Utilities to create class loaders.
 */
public class ClassLoaderUtils {
  public static URLClassLoader compileAndLoadJava(File root, String filename, String source)
      throws IOException {
    return withRoot(root).addClass(filename.replaceAll("\\.java", ""), source).build();
  }

  private static URLClassLoader createClassLoader(File root) throws MalformedURLException {
    return new URLClassLoader(
        new URL[]{root.toURI().toURL()}, Thread.currentThread().getContextClassLoader());
  }

  private static void writeAndCompile(File root, String filename, String source)
      throws IOException {
    File file = writeSourceFile(root, filename, source);

    compileClass(file);
  }

  private static File writeSourceFile(File root, String filename, String source)
      throws IOException {
    File file = new File(root, filename);
    file.getParentFile().mkdirs();
    FileWriter fileWriter = new FileWriter(file);

    fileWriter.write(source);
    fileWriter.close();

    return file;
  }

  public static ClassLoaderBuilder withRoot(File root) {
    return new ClassLoaderBuilder(root);
  }

  private static int compileClass(File sourceFile) {
    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
    return compiler.run(null, null, null, "-proc:none", sourceFile.getPath());
  }

  public static URL[] getClasspathURLs() {
    final String[] cp = System.getProperty("java.class.path").split(File.pathSeparator);

    return Arrays.stream(cp)
        .filter(str -> !str.isEmpty())
        .map(ClassLoaderUtils::parse)
        .toArray(URL[]::new);
  }

  private static URL parse(String fileName) {
    try {
      return new File(fileName).toURI().toURL();
    } catch (MalformedURLException e) {
      throw new RuntimeException(e);
    }
  }

  public static class ClassLoaderBuilder {

    private final File root;
    private final Map<String, String> classes;
    private final Map<String, String> resources;

    private ClassLoaderBuilder(File root) {
      this.root = root;
      this.classes = new HashMap<>();
      this.resources = new HashMap<>();
    }

    public ClassLoaderBuilder addResource(String targetPath, String resource) {
      String oldValue = resources.putIfAbsent(targetPath, resource);

      if (oldValue != null) {
        throw new RuntimeException(
            String.format("Resource with path %s already registered.", resource));
      }

      return this;
    }

    public ClassLoaderBuilder addClass(String className, String source) {
      String oldValue = classes.putIfAbsent(className, source);

      if (oldValue != null) {
        throw new RuntimeException(
            String.format("Class with name %s already registered.", className));
      }

      return this;
    }

    public URLClassLoader build() throws IOException {
      for (Map.Entry<String, String> classInfo : classes.entrySet()) {
        writeAndCompile(root, createFileName(classInfo.getKey()), classInfo.getValue());
      }

      for (Map.Entry<String, String> resource : resources.entrySet()) {
        writeSourceFile(root, resource.getKey(), resource.getValue());
      }

      return createClassLoader(root);
    }

    private String createFileName(String className) {
      return className + ".java";
    }
  }
  // ------------------------------------------------------------------------
  //  Testing of objects not in the application class loader
  // ------------------------------------------------------------------------

  /**
   * A new object and the corresponding ClassLoader for that object, as returned by {@link
   * #createSerializableObjectFromNewClassLoader()} or {@link
   * #createExceptionObjectFromNewClassLoader()}.
   */
  public static final class ObjectAndClassLoader<T> {

    private final T object;
    private final ClassLoader classLoader;

    private ObjectAndClassLoader(T object, ClassLoader classLoader) {
      this.object = object;
      this.classLoader = classLoader;
    }

    public ClassLoader getClassLoader() {
      return classLoader;
    }

    public T getObject() {
      return object;
    }
  }

  /**
   * Creates a new ClassLoader and a new {@link Serializable} class inside that ClassLoader. This
   * is useful when unit testing the class loading behavior of code, and needing a class that is
   * outside the system class path.
   *
   * <p>NOTE: Even though this method may throw IOExceptions, we do not declare those and rather
   * wrap them in Runtime Exceptions. While this is generally discouraged, we do this here because
   * it is merely a test utility and not production code, and it makes it easier to use this
   * method during the initialization of variables and especially static variables.
   */
  public static ObjectAndClassLoader<Serializable> createSerializableObjectFromNewClassLoader() {

    final String classSource =
        ""
            + "import java.io.Serializable;"
            + "import java.util.Random;"
            + "public class TestSerializable implements Serializable {"
            + "  private static final long serialVersionUID = -3L;"
            + "  private final long random;"
            + "  public TestSerializable() {"
            + "    random = new Random().nextLong();"
            + "  }"
            + "  public boolean equals(Object o) {"
            + "    if (this == o) { return true; }"
            + "    if ((o == null) || (getClass() != o.getClass())) { return false; }"
            + "    TestSerializable that = (TestSerializable) o;"
            + "    return random == random;"
            + "  }"
            + "  public int hashCode() {"
            + "    return (int)(random ^ random >>> 32);"
            + "  }"
            + "  public String toString() {"
            + "    return \"TestSerializable{random=\" + random + '}';"
            + "  }"
            + "}";

    return createObjectFromNewClassLoader("TestSerializable", Serializable.class, classSource);
  }

  /**
   * Creates a new ClassLoader and a new {@link Exception} class inside that ClassLoader. This is
   * useful when unit testing the class loading behavior of code, and needing a class that is
   * outside the system class path.
   *
   * <p>NOTE: Even though this method may throw IOExceptions, we do not declare those and rather
   * wrap them in Runtime Exceptions. While this is generally discouraged, we do this here because
   * it is merely a test utility and not production code, and it makes it easier to use this
   * method during the initialization of variables and especially static variables.
   */
  public static ObjectAndClassLoader<Exception> createExceptionObjectFromNewClassLoader() {

    return createObjectFromNewClassLoader(
        "TestExceptionForSerialization",
        Exception.class,
        "public class TestExceptionForSerialization extends java.lang.Exception {}");
  }

  private static <T> ObjectAndClassLoader<T> createObjectFromNewClassLoader(
      String testClassName, Class<T> testClass, String source) {
    final Path classDirPath =
        new File(System.getProperty("java.io.tmpdir"), UUID.randomUUID().toString())
            .toPath();

    URLClassLoader classLoader = null;
    try {
      Files.createDirectories(classDirPath);
      classLoader = compileAndLoadJava(classDirPath.toFile(), testClassName, source);

      final Class<?> clazz = classLoader.loadClass(testClassName);
      final T object = clazz.asSubclass(testClass).getDeclaredConstructor().newInstance();

      return new ObjectAndClassLoader<>(object, classLoader);
    } catch (Exception e) {
      throw new RuntimeException("Cannot create test class outside system class path", e);
    } finally {
      // we clean up eagerly, because it is fine to delete the class file once the class is
      // loaded
      // and we have no later life cycle hook here to do the cleanup
      tryClose(classLoader);
      tryDeleteDirectoryRecursively(classDirPath);
    }
  }

  // ------------------------------------------------------------------------
  //  miscellaneous utils
  // ------------------------------------------------------------------------

  private static void tryClose(@Nullable AutoCloseable closeable) {
    if (closeable != null) {
      try {
        closeable.close();
      } catch (Exception ignored) {
      }
    }
  }

  private static void tryDeleteDirectoryRecursively(Path directory) {
    final SimpleFileVisitor<Path> deletingVisitor =
        new SimpleFileVisitor<Path>() {
          @Override
          public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
              throws IOException {
            Files.delete(file);
            return FileVisitResult.CONTINUE;
          }

          @Override
          public FileVisitResult postVisitDirectory(Path dir, IOException exc)
              throws IOException {
            Files.delete(dir);
            return FileVisitResult.CONTINUE;
          }
        };

    try {
      Files.walkFileTree(directory, deletingVisitor);
    } catch (Exception ignored) {
    }
  }
}
